2011 Camry Hybrid Poor MPG

I have a 2011 Camry Hybrid with about 160,000 miles. For the last few months, the MPG has dropped significantly. It was 33mpg, but is now 24.7mpg.

No codes at all.

Spark plugs replaced 35K miles ago.
While no codes, I replaced the front O2 sensor.
Brakes were done about 20K miles ago.
Also air filter replaced.
Tires are Michelin fairly new.

Hybrid Battery: Does hold a charge over night, but when idling at a stop light, will rapidly go from a high charge down to purple.

I used Dr.Prius app, and blades are typically within 0.12 volts when idling, and about 0.24 - 0.30 when driving on the freeway.

No errors on the "overall battery test" and the life expectancy test indicates "fair" at about 54%

When driving, the live view shows green bars most of the time, occasionally yellow, and pretty even over time. Internal resistance is also pretty even, usually about 24 to 25.

I have ordered Prolong, thinking a recondition would help, as I was concerned about the SOC when stopped at a light, but this was also before I found out about DrPrius, which "seems" to indicate the battery is not "all that bad"...

Nevertheless, could the condition of the battery account for this degree of MPG loss?? 8 mpg is significant!!

Thank you for any thoughts or comments!

Andy

 

Followup:

I did another life expectancy test this evening. According to Dr.Prius app, I was never able to get the state of charge above 71.5, and when flooring the accelerator, the engine would drop to idle once the SOC was at 71.5. Annoyingly, the Dr.Prias app would not flip to the next step for some time, including after dozens of flooring/release of the accelerator.

Once Dr.Prius advanced to the discharge,I had great difficulty keeping the discharge in the green, due to the inverter/cooling fan popping on or off.

On this pass it said 50.86%, but also, "current overrun" tho I don't think it was more than the 20 seconds it indicated.


Performance: when starting from a dead stop like at a traffic light, almost any accelerator pedal pressure causes the ICE to immediately engage. Only the most gentle acceleration is battery only, and then only up to about 20 mph on flat and level.

Driving very conservatively I was able to improve the gas mileage slightly, but it just doesn't seem at all like it was previously.

thank you again for any cpmments.

 

I do all my own work on the vehicle.

Brakes were done some time ago, about 25k miles I think, and no indication of brake isues right now.

One of the things I did learn is that due to the "brake by wire" system, bleeding brakes using the techstream software is very important for calibration purposes, and if not done, drag does indeed result (as does premature brake failure for the rears, which I discovered the first time I replaced the rears—DOH!!!).

Since I will be installing the Prolong harness this week, I'll have a chance to carefully examine all of the busbars for corrosion. Though the vehicle is here in southern California (Hollywood) and not close to the beach, so I'm thinking corrosion is unlikely, but we'll see.

If they are corroded, do people use CLR? Soak the nuts and bus bars in CLR, and wire-brush the terminals? Is there an anti-corrosive that people like to apply and has had good results?

Thank you.

 

Indeed, as I indicated in my first post, I've gone through the other common issues.

No codes, no misfires. It's an 8 mpg loss in economy, i.e. about 25%.

 

More Notes and Prolong
Using the "Eco" display as a guide, in city driving in traffic, it won't get above 25. However, freeway driving with no traffic at 65mph, it's easy to get it to about 34mpg.

This is similar to the economy profile of the non-hybrid Camry, so my take away is that the ICE aspects of the vehicle are functioning just fine, and it therefore must be the hybrid system/battery that is causing the loss in MPG.

Prolong Arrived Today

The remainder of this thread, I will discuss Prolong Deluxe consumer charger/discharger with my Camry as a case study.

I'm not looking forward to installing the harness based on the documentation, but it's probably more time consuming than actually difficult.

Prolong First Impressions

Charger
The charger seems of good build quality, and I love the industrial design, which appears to be custom injection molded parts. It's a bit larger than I expected. Considering it's size, if it is a custom design, the tooling for the injection molds would be pricey, and makes me wonder what the size of the market is for such a device.

Discharger
A more conventional sheet metal box, and considering the amount of heat it must have to dissipate during a discharge, this makes sense—peeking through the air slots, the load is a big array of heat-sinked resistors.

Harness
I like that the connector is bright orange, not black like most of the photos pn the site. It does seem rugged, though it makes me slightly uncomfortable that 290V and 12V (fan) are on the same connector.

My one other concern is the inline fuse on the red lead, seems like it will be deep in the battery meaning if it blows, the battery needs to be disassembled to replace it. On the other hand, if the fuse holder were outside the battery, that might present other problems.

Next post: installing the harness.

 

So, I spent the last 5 ½ hours installing the harness, LOL… contributing factors are I’m old, still recovering from a minor surgery, and it was 98 degrees here… I’m sure a young wippersnapper could do it in less time.

A few things:

1) It's not necessary to remove the trunk rear panel. The driver's side of the trunk rear panel can be pulled away just enough to allow removal of the driver's side trunk trim panel.

2) it is not necessary to remove the rear seat backs, so I didn’t, thinking it would save time, but had I taken them out it might have been a little easier to do the work, and that might have saved more time.

3) I thought I could also get away with not unfastening the DC/DC converter, and while I did get the main cover off with the DC/DC in place, it was clear that I’d need to unfasten it to put the main cover back on.

4) The harness fit perfectly, the inline fuse located under the first (outer) battery cover.

5) However, the plug and play fan connector and green relay box don't have an obvious way to connect to anything to keep from rattling, I'm going to use strong velcro to attach the green box to the battery cover.

6) The Hybrid Auto Photo tutorial is overall pretty good, but there are few things that might be clearer, these photos are intended to embellish a few items:

SAFETY INTERLOCK/BATTERY DISCONNECT



Pull straight UP


Then pull towards you and down


Then pull orange connector completely out towards you.


SAFETY LOCK PIN

Align the battery disconnect handle so that the point on the end lines up to the hole in the safety lock pin, and so the indent in the battery disconnect handle lines up to the nub on the safety lock pin.


Hold the safety lock pin, and rotate the battery disconnect handle so the center part of the safety lock pin POPS UP.


Pulling straight up on the popped up piece will remove it from the hole.

 

Accelerated Single-Cycle Conditioning (Experimental!)

Yesterday's heat was brutal while I installed the harness. I waited for it to cool down a bit in the evening and then started a first fill/balance.

I had planned to start a full 3-cycle rebalance, but looking at the weather, more intense heat is expected the next two days. As a result, I decided to do only a truncated cycle with the aim of being done by 9AM, before the heat starts to rise excessively.

The charger brought the pack up to 286v (204 cell Camry Hybrid) and that was stable for at least half an hour or more. Then about 12:15AM I attached the discharger, and set it for 163volts.

The discharger started at about 1.5 amps, but under 246 volts or so, dropped to 0.5 amps. I decided to discharge only down to a cell voltage of about 1.06v (pack: 217v), mainly as it was about 4AM, and I wanted to get a high balance in before 9AM, and return the car to service 'till the ambient temps are more conducive to a series of full charge cycles,

To expedite, I disconnected the discharger, but did not connect the charger yet, instead, starting the car and using the ICE to bring the charge up rapidly. Using the Dr. Prius app, I monitored the SOC and the charging amperage, and tried to keep the charging above about 10 amps (Brake + In Drive + accelerator).

On bringing the SOC up to a reported 65%, I shut off the car, and connected the Prolong charger, and turned it on. It reported 287v, and the vehicle is now charging/balancing using the Prolong from here.

One factor that I felt this might be a useful shortcut for now, is the Dr.Prius app indicated the blades are all within 0.1 to 0.2 volts.

When the weather cools down, I will commence with the full 3 cycle recondition.

 

Multi-Cycle Prolong Recondition Begins Today

Step One
This morning about 4AM, put it on the charger. The ICE had already brought the battery up to about 70% per Dr. Prius. When I hooked up the Prolong charger, it indicated 286v and 0.375 amps

6 hours later, the charger still indicated 286v, with an occasional fluctuation to 287. This seemed as full as it's going to get right now, so connected it to the discharger, and selected the top, 163volt target. Discharger started at 286v and 1.45 amps.

The discharger is in the trunk on a box, with the heat exhaust pointed away from the vehicle.



Scheduling
I'm planning the timing here so that the charge cycles are done before noon, and the discharges are done in the afternoon, the thinking being that the charge/balance cycles should be done during the lowest ambient temperatures, but ambient is less critical for the discharge.

First Discharge

Starting about 11:30 am, discharge started with 286v at 1.45 amps (1.4 volts per cell)

About 2 pm it was 233v and 0.45 amps 1.14 volts per cell)

Now at 3:30pm, 204v and 0.27 amps (1.0 volts per cell)

Hard to guess how long to 163 volts as this part of the discharge curve is increasingly non-linear, but I’m going to check every hour.

At 4:30pm, 190v and 0.268 amps. I'm going to guess a little less than two hours to 163.

At 5:30, 178v … I took a look at block voltages using Dr Prius app (not running vehicle, just pressing start twice without touching brake-this turns on car but not the hybrid system). Here’s a screen shot:



What strikes me most is the wide variation between blades at this discharge level. Per this, then some cells are clearly already below the 0.8v per cell target for the first discharge.

researching the topic further, for a single NiMh cell, a single cell can be brought to 0v. The trouble is in packs, if a cell is 0v but others are higher, they can push the weaker cell into reverse polarity that can cause permanent damage.

In the present case, the discharge current is very low, and I’ll be charging immediately when complete. I’m putting some faith into hybrid automotive’s approach here, as I know this system is widely used, and successfully.

At 6:30pm: DONE. Well, like I said, non-linear. I missed seeing it hit 163, as it was already rebounding, the discharging light blinking. When it flipped to idle, there was no buzzer as the manual said there would be.


Charge Cycle Two

So, reconnected the Prolong charger, and started the charge… here it started at 183v (the rebound voltage).

But weird: the ammeter is fluctuating all over, from 0.62 to 0.018 up and down. I have a video I’ll post at some point.

At 7pm, after charging about half an hour, this is what Dr.Prius app looks like:



The ammeter on the Prolong still fluctuating from about 0.59 to 0.018 … I’m hoping this is normal, I don’t see it as to be expected in the documentation, but the battery is clearly charging.

I’m also concerned about the very wide spread in blade voltages, compared to when operating and before starting the process. While documentation and support said that a full balance overcharge is not needed until after the last discharge, I’m inclined to let that happen on this cycle before proceeding to the deeper discharge of 0.6v per cell.

———
Fifteen minutes later at 7:15pm, the ammeter fluctuations are now more reasonable at 0.67 to 0.37 with the voltage at 227v.

Looking at the Dr. Prius app, the feels that are lagging behind are most very different than I expected, except block 7. Block 6 and 14 are surprising to me, and I hope there was not a reversed cell in those blocks.

On the positive, the voltage spread is decreasing.



7:30pm pack is up to 240v, ammeter is 0.5 to 0.02. … hmmmm

But the charge is progressing and voltage differences narrowing:



8:05pm, the pack is close to operating range at 243v. Ammeter tho is still fluctuating a lot. Blades are all a lot closer… except #16 now. Weird.



8:30 pm - voltage is now above the operating range of 246v. It’s at 248v and now the ammeter is stable at 0.378 amps. Now all the blades are within 0.22 volts:



At the present rate of charge, I expect it to be at the top I.e. 286v in about an hour, maybe two?

The question I’m asking myself now is, do I let it balance for 4 to 6 hours before discharge? And when I discharge do I go down to the next lower level of 123v or do I stick to the more conservative 163v ??

I’ve read on some forums that the 0.8v per cell is safest and realize the major benefit, and the 0.6 or 0.5 is riskier and not necessarily of greater benefit. Documentation from several battery manufacturers seem to echo this, but Hybrid Automotive does recommend the three stage all the way to 0.5v — and I notice that they did at one time have the third level down to 0.1v per cell (their former “intelligent charger” which is no longer offered??)

9:30pm: pack voltage is 261v, ammeter is stable at 0.378 amps. I guess another hour or so to fill.



Voltages now within 0.12 to 0.22, and we’re also back to seeing #7 as the (apparently??) weakest block.

10pm - 265v, it seems charging has slowed tho still at the same 0.378 amps… only adding at the rate of 8v/hr to the pack charge. At this rate, I’d expect another two to three hours, and I’m gonna guess that charge rate will slow further.

10:30pm: 268v
11pm: 270v
11:30pm: 272v -- at this rate, 286v will probably be around 7am. I'll return then for followups.


Updates will be edited into this post live as they happen.

 

Charge cycle two continued.

6am —just now tipping into 286v, current at 0.375 … Dr.Prius app shows 285.75. So 4 to 6 hours from here for balancing, and this is on the planned schedule of the discharge starting near noon each day.

Notice in the Dr.Prius screen, voltages are much tighter (0.07 to 0.12) also notice the internal resistances are lower than earlier this week. Battery temps are a bit higher now, indicating some cells are reaching full charge/overcharge.


12:30pm — been balancing for over 6 hours no change in voltage. 286v and 0.375 amps.





I’m going to let it rest for 15-20 minutes then start the discharge cycle. While the documentation only mentions a rest before driving, it seems to make sense to me that some rest interval would be good between each charge and discharge. I’m curious if there are any opinions on this.??

1 pm : started discharge. The rest brought the voltage down to 284, and the discharge started at 1.437 amps… I selected the 122v target.


Dr.Prius app under the discharge load, a few minutes in:



2:30 pm — the discharge hit 246v, but still at 1.43 amps. I was expecting this to be the point it dropped to 0.5 amps, but as I selected the 122v target, perhaps it stays at 1.45 a little longer?



2:40 pm — at 243v, the discharge ammeter started fluctuating, up and down about 1.2 to 0.75 amps.

Useful note: this discharge cycle is taking notably longer than the previous one, this is good news!

2:55pm — close to 242v, with current stabilizing at the 0.49 rate.

So it appears; with cell voltages above 1.2v, discharge is 1.47 ish, and then reduces so when the cell voltages are at 1.19v, discharge is 0.49 amps.

Then based on the last example, I’ll guess that the drop to 0.27 amps is at cell voltage 1.0.

And I wonder if there’s a further drop at 0.8, which was the previous target (163v).

3:04pm DrPriis sample. This discharge is taking longer than the last one.



3:30pm — 237v and the voltage difference is slightly higher, now fluctuating 0.12 to 0.33 v.



4:30pm — WOW! At 214v, and the voltage difference is only 0.56. On Friday, in the accelerated trial cycle, at 2.14v the discharge, was 2.61 !!!!



I am now very curious to see what the voltage difference is when we’re down in the 170v area.

5pm — 200v and 0.27 amps. Per Dr.Prius the voltage difference has increased to 1.07v — while higher than I was hoping it is still substantially improved from yesterday.


5:30pm — 182v and voltage difference has risen to 1.6.


5:45pm — 171v and 0.258 amps

6pm — 163v and 0.258 amps. Volt difference has risen to over 2.76v



This will continue in the next post…

 

Prolong on a 2011 Camry, continued.

Wrapping up discharge cycle 2

Okay, so voltage is dropping rapidly now, about the rate of 1 volt per minute. Current is 0.25 or so.

at 6:06pm, 157v and a diff. Of 2.9v

6:15pm — 150v and volt diff of 3.2v


6:22pm — 144v and diff 3.4v


6:30pm — 137v and diff 4.05v


Discharge final moments, starting at 6:35pm, one per minute:




I didn’t actually see it touch 122v, then started rebounding quickly.



after rebounding to above 164, I connected the Prolong charger. These are one minute slices until it reached 204v (1v per cell) shortly before 7pm:



7pm — 209v and diff of 2.0v …. Also, a meter is fluctuating as before.



7:30pm —240v and diff has dropped down to 0.37… a meter still fluctuating 0.02 to 0.4 or so… yesterday, it didn’t go solid until about 246v.



8pm — 241.5v and current still fluctuating… volt diff is about 0.3



On Expediting: I’d like to be done by 7am tomorrow… I do have other things to deal with…but I want to get in a good long 6 hour balance… so I’m thinking once the pack is over 246v, I use the ICE to charge at 10 amps to get the voltage up close to 286, and then let it balance on the Prolong charger.

I believe the Prolong Pro gear does have a high charge rate for the “middle range” if I’m not mistaken. But I am wondering if there is any downside to using the ICE to charge from 248 to 284 or there abouts…

8:30pm — 244v with 0.27v difference


10pm — 264v and 0.15v difference, also current is stable at 0.377 amps.







Updates added to this post as they happen…

 

Final Fill and Balance

Expediting the fill stage
I had to be done by 7am, so after the Prolong charger brought the pack voltage well into the operating range, and the current stabilized, I turned it off and used the ICE for the remainder of the fill portion of the charge. This seems to have had an added benefit: the internal resistances are all now at 19, where they were 21-23 before.

Dr.Prius just before switching to the ICE for charging:



Starting the car, pressing the brake, and putting it in drive:


I probably did not have to put it in drive to force the charging, as I had turned the car on without starting (two pressed of the Start button with foot off the brake) several times in order to user Dr. Prius. As a result, the hybrid system eventually set the SOC to 0.

With the SOC reading below 40, when the car is started the ICE will always come on to charge regardless.

In the present case, I let it run for 15 minutes, and the charge amperage was between 8-10 amps. This brought the reported SOC to 50%, till the pack voltage read 292v.The battery temp increased a bit to about 96°F, and I shut off the ICE and let the battery rebound, and it came back down to about 283v.




I then turned the Prolong charger back on to complete the fill and balance.




This Morning

6:15am - pack voltage was 288v, current was 0.377, and voltage difference between blocks was about 0.10v per Dr.Prius.




Over the next 45 minutes, it appeared that the pack was increasing in charge by 0.2v per hour.




7am -- Turned off and disconnected the Prolong charger. The battery rebounded to 286v.




NEXT: looking at mileage and performance after driving later today.

 

Driving Today:

RESULTS: In mixed freeway and city stop-n-go driving, the MPG on the dash indicates 33mpg over the last 100 miles or so.

FACTORS: In addition to the battery recondition:

• I noticed the cabin air filter was gross and undoubtedly causing the A/C to work harder than needed (I had been setting it at LO all the time recently). Replacing the cabin filter and suddenly the vents were blowing a proper amount of air, and I could set a reasonable temperature (which also allowed using the A/C Eco setting).

• I ran two Techron High Mileage in the last two tanks of gas (half tanks each).

• I am driving more conservatively.

Recalibration and Performance Notes
I disconnected the battery cable after letting the car rest for some time after the charge. This was to reset all codes and also any weird battery calibrations.

As a result, some time was needed for the hybrid system to "recalibrate" the battery. It seemed that performance wasn't much better until the newly reconditioned battery was recalibrated.

Early in the day, I couldn't really drive on hybrid battery only, the ICE would always kick in. By the end of the day though I was easily driving up to 25mph on flat/level on battery only.

Also, while accelerating "normally" (i.e. not super gentle) the ICE would kick in right away, as before the recondition—however it is definitely much smoother. Before the recondition, when starting from a dead stop, the ICE would seem to strain and struggle, and run rough until up to speed.

This I assume is due to the Atkinson cycle having poor low end torque. To me this means that before the recondition, there was little hybrid assist, and this certainly would explain the poor fuel economy.